### Please describe the problem.
Some internals of git annex does not check if the shell it is running is Posix-compatible, ie. bash.

I am using fish, and after setting up local pairing, and working, I switched back the login-shell to fish, and when syncing a file, I got this error, read from daemon.log:

fish: Unknown command 'GIT_ANNEX_SHELL_DIRECTORY=/home/s/annex'. Did you mean to run ~/.ssh/git-annex-shell with a modified environment? Try 'env GIT_ANNEX_SHELL_DIRECTORY=/home/s/annex ~/.ssh/git-annex-shell...'. See the help section on the set command by typing 'help set'.
Standard input: GIT_ANNEX_SHELL_DIRECTORY='/home/s/annex' ~/.ssh/git-annex-shell
                ^
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.

### What steps will reproduce the problem?
Set up local pairing ( I believe having sh/bash as login terminal is necessary for this).
Switch back to fish as login-shell with chsh -s /usr/bin/fish
Add a file to either repository.

### What version of git-annex are you using? On what operating system?
[s@b ~]$ git annex version
git-annex version: 5.20140320-g63535e3
build flags: Assistant Webapp Webapp-secure Pairing Testsuite S3 WebDAV Inotify DBus XMPP DNS Feeds Quvi TDFA CryptoHash
key/value backends: SHA256E SHA1E SHA512E SHA224E SHA384E SKEIN256E SKEIN512E SHA256 SHA1 SHA512 SHA224 SHA384 SKEIN256 SKEIN512 WORM URL
remote types: git gcrypt S3 bup directory rsync web webdav tahoe glacier hook external

### Please provide any additional information below.

[[!format sh """
# If you can, paste a complete transcript of the problem occurring here.
# If the problem is with the git-annex assistant, paste in .git/annex/daemon.log


# End of transcript or log.
"""]]

> [[fixed|done]] so
> 
> I have not tried to make the assistant go back and fix up existing
> `authorized_keys` lines. So if someone had been using a posix shell and
> switched to fish, they'll hit this and need to fix it themselves. I judge
> this is pretty small number of users. --[[Joey]]